AMBIDENT HETEROCYCLIC REACTIVITY - THE ALKYLATION OF PYRROLOPYRIDINES(AZAINDOLES, DIAZAINDENES)

7-Methyl-6-azaindole, 7-acetamido-4-azaindole, the substituted 4-amino -, 2-methyl- and 6-methyl-7-azaindole, and the parent 4-, 5-, 6-, and 7-azaindole systems (as anions in dimethylformamide) were alkylated wi th a variety of primary alkylating agents. The relative importance of charge, product development, and steric approach control in determinin g the alkylation pattern (pyrrole versus pyridine ring alkylation) are discussed within a framework of variable S(N)2 transition state struc tures. Frontier orbital factors appear to be relatively insignificant. The charge distribution, orbitals and energetics of these heterocycli c systems were modelled by ab initio molecular orbital calculations (S TO-3G level). Specific association, involving hydrogen bonding between adjacent groups and the alkylating agent, is important in determining the alkylation pattern in some cases.